An automatic manual transmission comprises at least one servo-assisted clutch and a gearbox, which is coupled to the clutch and comprises, in turn, at least one primary shaft, which is adapted to receive torque from a drive shaft of the internal combustion engine, at least one secondary shaft adapted to transmit torque to the drive wheels, a plurality of pairs of gears, each of which defines a corresponding speed and comprises a primary gear mounted on the primary shaft, and a second gear mounted on the secondary shaft and permanently meshing with the primary gear, and a plurality of servo-assisted locking devices (the most common of which are synchronizers), each of which is mounted on a shaft and is adapted to be actuated to lock at least one corresponding gear to the shaft itself. Normally, each locking device is arranged between two gears to engage both the gears in an alternate manner.
The number of pairs of gears increases along with the number of gears, and consequently so does the number of locking devices in the measure of one further locking device for every two additional gears (in the most favorable case in which the total number of gears is an even number). It is thus apparent that increasing the number of gears causes an increase of size, weight and cost of the gearbox.
Patent application DE102010050126A1 describes a vehicle transmission comprising:
a mechanical gearbox, provided with a primary shaft, which is adapted to receive torque from an internal combustion engine, a secondary shaft adapted to transmit the torque to front drive wheels via a differential, and a plurality of pairs of gears, each of which defines a corresponding transmission ratio;
a servo-assisted variable transmission ratio transmission device which is arranged between the secondary shaft of the mechanical gearbox and the differential and is adjustable to have two different transmission ratios L and H; and                a control unit which drives the servo-assisted transmission device and establishes which transmission ratio to select as a function of the vehicle speed and/or the drive wheel load.        
However, the transmission described in patent application DE102010050126A1 has a relatively high weight and large dimensions; consequently, such a transmission is complex to arrange in a high performance road car.
Overview
The present subject matter relates to an automatic manual transmission for a car provided with an internal combustion engine, which automatic manual transmission is free from the drawbacks described above, is easy and cost-effective to make and, in particular, allows to obtain a high number of gears with small size, light weight and low cost.
According to the present subject matter, an automatic manual transmission for a car provided with an internal combustion engine is provided as disclosed in the accompanying claims.